INVESTIGADORES
CHAVERO Carolina Andrea
artículos
Título:
CD-62°1346: an extreme halo or hypervelocity CH star?
Autor/es:
PEREIRA, C.B.; JILINSKI, E.; DRAKE, N.A.; DE CASTRO, D.B.; ORTEGA, V. G.; CHAVERO, C.; ROIG, F.
Revista:
ASTRONOMY AND ASTROPHYSICS
Editorial:
EDP SCIENCES S A
Referencias:
Lugar: Paris; Año: 2012 vol. 543 p. 1 - 14
ISSN:
0004-6361
Resumen:
Context. High-velocity halo stars provide important information about
the properties of the extreme Galactic halo. The study of unbound and
bound Population II stars permits us to better estimate the mass of the
halo. Aims: We carried out a detailed spectroscopic and kinematic
study and have significantly refined the distance and the evolutionary
state of the star. Methods: Its atmospheric parameters, chemical
abundances and kinematical properties were determined using
high-resolution optical spectroscopy and employing the
local-thermodynamic-equilibrium model atmospheres of Kurucz and the
spectral analysis code moog. Results: We found that
CD-62°1346 is a metal-poor ([Fe/H] = -1.6) evolved giant star with
Teff = 5300 K and log g = 1.7. The star exhibits high carbon
and s-element abundances typical of CH stars. It is also a lead star.
Our kinematic analysis of its 3D space motions shows that this star has
a highly eccentric (e = 0.91) retrograde orbit with an apogalactic
distance of ~100 kpc, exceeding by a factor of two the distance of the
Magellanic Clouds. The star travels with very high velocity relative to
the Galactocentric reference frame (VGRF = 570 km
s-1). Conclusions: CD-62°1346 is an evolved giant
star and not a subgiant star, as was considered earlier. Whether it is
bound or unbound to the Galaxy depends on the assumed mass and on the
adopted Galactic potential. We also show that the star HD 5223 is
another example of a high-velocity CH star that exceeds the Galactic
escape velocity. Possible origins of these two high-velocity stars are
briefly discussed. CD-62°1346 and HD 5223 are the first red giant
stars to join the restricted group of hypervelocity stars.